Rocket propellants and their utilization



p less at ratios below Pitenidaul 15,1958 7 ROCKET .PROPELLANTS AND THEIR I TI IZATION Arnold L. Ayers, 'ldaho Fall :Idaho,and Cleveland R. i

Company, 'a corporation of Delaware No nmwing. A lications lays, 1 9-52 1 Serial No,287,028

1-7 .Claims. (61.60-35. 1)

Scott, Bartlesville, flkla assignorsto Phillips Petroleum -i This invention relatesto rocketpropellants: In ZOIlB Our invention is concerned with new and novel rocket propellants and ztheir utilization; a rocket or jet'propulsion device, being defined herein as a'rig'id container "for matter and energy so arranged that a portion of the mat er can absorb the energyrin kinetic :form tand'subsee' .quently be. ejected in va specified direction.

'rocket to which our invention is ap'plicd is that type of V jet propulsion device designated as a pure rocket, i. e.,

I ai -thrust producer'which does not make .use of the sur The type is" Q embodimentthis invention relates to hypergolic fue s land their application to the propulsion of rockets.

'hypergolic combustible materials. to provide fuels that are hy'prg'olic when contacted with I considerations may necessitate the use of higher ranges, even as high as 6E1. e An object of this inventionis to. provide-new rocket propellants. Another object is toprovide a methodafor producing thrust toa rocket; Another object'is' -topro- Y videnew hypergolic fue'lsf, Another object is to provide fuels that are hypergolic even when diluted with non:

white furning nitric acid.;. Anotherobject is to provide fuels that are hypergolic, when contacted with red fmning nitric acid. Another 'Obiect'is', to, provide a gronplof conjugated diene-r'nonomers and polymers. of such dienes asnew hypergolicfuels, Another object is toprovide lg3-hutadiene, '2-rnethyl-'l,3butadiene, 11,3 pentadiene and selected liquid polymers of ll,3-bu.ta.dieneo asflalpre; ferred group of new hypergolic fuels. .Other objectswill be apparent to thoseskilled in the art Ein. the light 'of lthe accompanying discussion: and disclosure In accordance with our invention We have provided rocket bip'ropellant materials, the fuel components. of

rounding-atmosphere. A roeketjof the 'type'with which our inventionis "concerned is propelled by introduction of j-apropellant material 'into'a' combustion chamber therein, and-burning it under conditions that will cause 'which are selected from atleast one of thengroup consisting' of (1') {a conjugatedjdiene characterized -.b yjthe structural formnla. j J

I V wherein one R is a radieal 'selected from the group eon iti to' release energy at a high but controllable rateqim- 2 it mediately afterent'ry into the combustion chamber.

Roeket propellantsjas liquids, are advantageously utilized'ina'smuch as liquid propellant 'materia'ls can be caririe'diin a, lightweight low pressure vessel and pumped into the combustion chamber, thel'atter though "it must withstand high pr'es s'ure andternp erature, being" only necessarily largeienough to insure combustion. :Sc ondly, the flow ofliquid propellant into the combustion chamber, can beregulatedat will so that the thrustjcontinuous or in intermittent bursts of .power, can be sus- I tained, the latter type of liquidpropellant flow contributing to a long lifeof the combustion chamber'and thrust nozzle. r v t Various liquids and liquid. combinations: have-been V found useful ,a' sirocket propellants. Some propellants "sist of 'a single liqnid, and are 'terrned'fmonopropellants. -Those propellants involving two liquids are termedfifrbipropellants and normally consist of an oxir dizer aiid'a fuel. Hydrogen peroxide andnit'romethane are eaohtwell known monopropjellants. Well known bipropellants include hydrogen peroxide orliquid oxygen as the oxidants,- witha fuel component such as ethyl alco hol-water,"ammoniafhydrazine, or hydrogen; and nitric acid as the oxidizer with aniline or' furfura'l' alcohol as I hypergolic bipropellant fueldmponents.

/;-When -e rnploying 90-100 percentznitric acid, 'i.{.e., .fwhite fuming nitric acid asf-the oxidizer in *a rocke't 7 bipropellant, it is oftennecessary, dependent on thespe fcifig fuel tcornponent, to i'make ignition :more' prompt by' b "dissolving from 6. to 1 4-percentof nitrogendioxide-in the -White fuming nitric. :acid. forming thereby 'red -fuin J ing? nitric acid. A fuel component of a bipropellant material-of the type described herein, is spontaneously cljiippn contacting .theoxidiz'erf, and {for thatreason mixed acids, particularlyqimixtures"sof'nitricrand sulfuric V b our. hypergolic fuel components! retain their hypergoli is. ef red to herein as being hypergolic. A ratio of oxidizer to hypergolic fuel based on stoichiometric amounts can beutilized, withinjthe limits of 0.5:1Mto.

v v he ieor'lihustionilaeing' r p "eat-the oxidizer bei g; less economical at ratios above 1.1., However, practical sisting of-H, phenylf substituted alleyl, substituted phenyl, auaoxy, N05, and each remaining R is -selected from the g roupconsis'ting of H, andi'an' 'alkyl; group containing not 'morethan '4 carbon atoms, the maximum number of carbon" atoms in the total'Rs-notiexceeding 12 and 2) laliquid open-chain polymer of said conjugated die ne characterized by a viscosityi at enerallyrmm 5 it 1(),00( )1:Saybolt "Fur'olse co'nds; and a molecular weight generally withinthe lirnits of from 200 to 10,000 asdetermined by the freezing point lowering of benzene. j The fuel components of our invention are-'hypergolic alone and also 'whendilnted' with nonfhypergolicfcom bustib'le' materials-such as n-he'p'tane, hydrocarbons boiling in the gasolinerange, kerosene,"'isooctane, -diisobutyl ene, methylcyclohexane, benzene, toluene, and ,the' like;

indilutions containing as'*high as 60 percentofthejnonf Any known soxidiz er' components may be" I, bipropellantssof' our invention, particularly ethereal dants,such asnhydrogen. peroxide, liquid oxygen, and

a i v r v-Further' illustrative vofzthe.'hyp'ergolie-fuels of our inventionare -1-- ,to1yl-,,,j b adiene; ilisopropylphenybi,3- adi ne ziZ-e hyJPhQykl-p ntad ene o pentadiene, 3-nitro-l,3-hexadiene, 2,4-heptadienel 2f3 dimethyl-l,3-butadiene, ;2,4 -octadiene, 3- bntoxy-2,5-hexadiene,

V prefer to employ as :hypergohc fuels in accordance With ourinvention, materialsselected from the g oupl n st n l,3 utadiene,' 'f2-methy1-'i,3

butadiene free'fi oin s ldfpolyrne'rs,andfhaving a Wis", i cosity within the limits lf'S' a'ndfiOOO SFS as rneasured pentadieneare produced by'jvarious known methodsas; for;-.exa-mple- =by -hydr'ocarbon cracking and are. generally Another ,object din he present as by-products in various hydrocarbon cracking processes in particular directed toward the production of dienes. One well known method for the preparation of 1,3-butadiene .involves the dehydrogenation of n-butane to produce butenes followed by dehydrogenation of the but ene product to form the 1,3-butadiene. j .The liquid diolefin polymer employed as a hypergolic fuelin accordance with our invention is not a rubber-like synthetic polymer, but rather it is a liquid and is characterized by the viscosityand molecular weight limitation already described. The liquid polydiene fuel component of our invention can be prepared in any desired manner. For example, such a liquid polymer can be prepared from .1,3-'butadiene by emulsion polymerization of, 1,3- .butadiene in the presence of a sufiiciently large amount of modifier, such as 3 to parts by weight of an alkyl mercaptan' per' 100 partsof'the butadiene monomer to be polymerized, or itmay be'pr'epared by bulk or homogeneous polymerization of the diene monomer in the presence of a finely divided alkali metal catalyst and a modifying solvent. One such method is disclosed in application Serial No. 67,098, W. W. Crouch, filed December 23, 1948, now Patent 2,631,175, issued March 10, 1953. In accordance with the procedure referred to inthat copending application, the preparation in a preferred modification comprises the steps (1) removal of deleterious materials from the diene monomer feed, (2) polymerization of the diene in the presence of an alkali metal catalyst and a suitable diluent, the reaction being carried out under carefully controlled reaction conditions, particularly temperature, catalyst condition and concen- ,tration,.quantity of solvent and'rate of addition of the monomeric diene to'the polymerization zone, and (3) recovery of theliquid diene polymer so produced. When conducting the polymerization in this manner a polymer is produced comprising a substantially colorless transparent liquid having a viscosity not exceeding 10,000 Saybolt Furol seconds at 100 F, and a molecular weight within the limits of 200 and 10,000 as determined in accordance with the freezing point lowering method employing benzene. The double bonds of the liquid polymer thus produced are of such a nature that they do not react completely under conditions ordinarily used for iodine number determinations and therefore this method for determining unsaturation is not reliable. However, the unsaturation has been determined by an iodine monochloride method which gives more significant results. For example, a molecular weight of a given sample of liquid polybutadiene of 2000 was assumed, and the unsaturation was foundto be in the neighborhood of' about 30 double bonds per molecule. This is equivalent to an iodine number of about 371. Stated in a different way, that polymer on this basis was calculated to contain 0.79 double bonds per butadieneunit.

The advantages of this invention are illustrated in the following examples. The reactants and their proportions and their specific ingredients are presented as being typical and should not be construed to limit the invention unduly. p

' Example I Eachofthe conjugateddiolefins describedhereinbelow was tested at room temperature for spontaneous ignition, employing nitric acid as the oxidizer. In conducting these tests 0.13 ml. of a mixture (with one exception) of the conjugated diolefin and pure grade n-heptane was dropped into a l x 8" test tube containing 0.3 ml. of either red or white fuming nitric acid. The diolefin and the nitric acid, in each test, ignited spontaneously upon coming in contact with each other in'the test tube. The pure grade n-heptane was employed to determine the maximum amount of dilution that such a diolefin would tolerate and still retain its hypergolicity. Results of tests using '4 1,3-butadiene, 2-methyl-l,3-butadiene and 1,3-pentadiene are recorded in the following table.

1 Dilution was not attempted due to the difilculty of handling the low boiling 1,3-butadiene.

Example II 1,3-butadiene and 2-methyl-1,3-butadiene were tested in accordance with the procedure of Example I, except that a diluent was not employed, and the tests were carried out at 40 F. Results of these tests are tabulated as follows:

Compound Oxidant Diluent Result 1,3-butadiene R21 idFuming Nitric None Ignition.

c 2-methyl-1,3-butadiene.. do do.. Do.

Example II A sample of liquid polybutadiene was prepare by the batch polymerization of 1,3-butadiene as a 30 to 40 weight percent mixture of butadiene in n-heptane employing a 1.25 weight percent suspension of sodium in finely divided form, sometimes referred to as sodium sand, in xylene as catalyst. Polymerization was effected at 200-205 F. for three hours. The catalyst was inactivated by addition of methanol and the polymer solution treated with dilute sulfuric acid and washed to remove sodium residues. The polymer was recovered by removing the solvent by' distillation. The polymer had the following physical properties and analysis:

Viscosity, Saybolt Furol seconds at F 435 Gardner color l0 Specific gravity, 60/ 60 F 0.9097 Refractive index, 68 F 1.5200 Flash point, Cleveland open cup method F 280 Ash, weight percent; 0.013 Volatiles, weight percent 0.87

' This liquid polybutaciiene was found to be hypergolic in the presence of both red and white fuming nitric acids. Results are recorded below.

' 7 Maximum Compound Oxidant V Dilution,

Percent n-Heptane Liquid polybutadiene-.- White Fuming Nitric Acid 60 Do Red Fuming Nitric Acid 40 Example IV Z-methoxy butadiene was tested for spontaneous ignition employing both white fuming nitric acid and red fuming nitric acid, as the oxidizer. These tests were conducted in accordance with the test procedure of Example' I, at both 40 F. and at room temperature (about '70' F.). Results of these tests are tabulated as follows:

Temperature Oxidant. Dilution Percent n-Heptane.

" Red fuming nitric acid 30 White fuming nitric acid '30 Red fuming nitric acid 10 White fuming nitric acid 10 escaped As an added featureofthis invention the bipropellant" fuel components described hereinabove' are also useful q Pro in ast. bur ing. ue -s i ab e or s n. rocket engines andthe like wheije a hypergglic fuel; is not nec-v sa b s u sq- Fo x ma e. at l; component of this invention dissolved in a liquid hydrocarbon, such a gasoline, a jet fuel, a kerosene, a naphtha, or a petroleum fraction having a boiling point usually not greater than 800 F., even if the resulting solution is not hyperoglic with an oxidant such as fuming nitric acid, can be used together with an oxidant and a suitable ignitor as a rocket propellant. These fast burning fuels are particularly useful if for various reasons a hypergolic fuel is not desired or required. The fuel components described, may be added to a hydrocarbon liquid in a minor'amount, usually from about 1 to 20 percent'by volume of the total admixture to produce fast burning fuels. Suitable fuels are 1-20 percent by volume of the selected fuel component and 80-99 percent by volume of a petroleum fraction of the type described above, often a normally liquid hydrocarbon mixture boiling up to an end point of about 425 F., i. e. a gasoline fraction.

Variation and modification are possible within the scope of the foregoing disclosure and the impended claims to the invention, the essence of which is that certain conjugated dienes, and liquid polymers of such conjugated dienes have been found to be hypergolic, and to be useful. for providing fast burning fuels suitable for use in rocket engines.

We claim: V

'1. A method for producing immediate thrust to a rocket, comprising introducing oxidizer and fuel of a bipropellant into said rocket in contact with each other in a combustion zone therein in proportions so that.

1' to fuel being within the limits from 05:1 tater, and burning said fuel in said rocket wit-h said oxidizer iatia high but controllablerate, saidfuel containing: front 1 to 100 percent of a component which is hyp'er'goli'c. in-

the pure state when contacted with said oxidizer, said component- 7' being an essenti-al ingredient for imparting said fast burning; quality to, saidfuel by its presence therein, said component being at least, one of the materials, selected from the group consisting of V (1.). on- 7 jugated' 'diene characterized by the structural'formula 7 sisting of H, phenyl, alkoxy, N0 and each remaining R is selected from the group consistingof H, and an alkyl radical containing not more than 4 carbon atoms,

spontaneous ignition is efiected and burning said fuel in said rocket, said fuel comprising at least one fuel component selected from the group consisting of (l) a conjugated diene characterized by the. structural formula ju'gated diene and characterized by a viscosity at 100 F. of from 5 to 10,000 Saybolt Furol seconds, and a molecular weight within the range of from 200 to 10,000 as determined by the freezing point lowering of benzene.

2. The method of claim 1 wherein the stoichiometric ratio of oxidizer to hypergolic fuel is within the limits of 0.5:1 to 15:1. I V

3. A method for producing immediate thrust to a rocket, comprising introducing oxidizer and fuel of a bipropellant into said rocket in contact with each other in a combustion'zone therein in proportions so that spontaneous ignition is effected and burning said fuel in said rocket, said fuel comprising 1,3-butadiene;

4. The method of claim 1 wherein said fuel component is 2-methyl-l,3-butadiene.

5. The method of claim 1 wherein said fuel compoent is 1,3-pentadiene,

6. The method of claim 1 wherein said fuel component is a liquid polybutadiene characterized by a viscosity within the limits of 5 and 6,000 SFS at 100 F.

7. A method for producing immediatethrust to a rocket, comprising introducing an oxidizer, which oxidizer is capable of causing spontaneous ignition upon contact with a hypergolic fuel, and a fast burning fuel 'into, said rocket in a combustion zone therein in contact with each other, the stoichiometric ratio of oxidizer the maximum number of carbon atoms in the total Rs not exceeding 12, and (2) a liquid polymer of said conjugated diene and characterized by a viscosity at F. of from 5 to 10,000 Saybolt Furol seconds, and a molecular weight within the range of from 200 to 10,000 as determined by the freezing point lowering of benzene.

8. A method of claim 7 wherein said fuel containsa combustible liquid hydrocarbon fuel material, which material is not capable of spontaneous ignition in the pure state when contacted with said oxidizer, as a diluent for said hypergolic' component, said material being pres- 'ent in such an amount relative to said hypergolic component that said fuel is not capable of spontaneous ignition upuon contact with said oxidizer. V

9. A method of claim 1 wherein said fuel contains a combustible liquid hydrocarbon diluent, which material is not capable of spontaneous ignition in the purepstate upon contact with said oxidizer, said diluentbeing present in an amount permittingsaid spontaneous ignition to be effected.

10. A method of claim 8: wherein said liquid hydrocarbon is a n-parafiin.

11. A method of claim 8 wherein said liquid hydrocarbon is benzene.

12. A method of claim 9 wherein said liquid hydro- V 7 carbon is a n-parafiin.

13. A method of claim 9 wherein said liquid hydrocarbon is benzene.

14. The method of claim 8, wherein said fuel contains wherein one R is a radical selected from the group consisting of H, phenyl, alkoxy, N0 and each remaining R is selected from the group consisting of H, and an alkyl containing not more than 4 carbon atoms, the maximum number of carbonatoms in the total Rs not exceeding l2, and (2) a liquid polymer of said conjugated diene and characterized by a viscosity at 100 F. of from 5 to 10,000 SP8, and a molecular weight within the range of from 200 to 10,000 as determined by the freezing point lowering of benzene, said essential ingredient comprising from 1 to 100 percent of the combustible fuel present in said rocket propellant, and burning said compound in a combustion zone of said rocket with an oxidizer, said oxidizer being capable of causing spon- 7 8 taneous ignitionupon contact with a hypergolic fuel in 2,573,471 Malina et a1. Oct. 30, 1951 the pure state, the stoichiometric ratio of said oxidizer to 2,631,175 Crouch Mar. 10, 1953 combustible fuel in said ocket propellant being in the 2,712,497 Fox et a1. July 5, 1955 range from 0.511 to V r O References Cited in the file of this patent S t 'lg at lJoumal 1 8 f3? Rocket 1 ep em er pages A UNITED STATES PATENTS Leonard: J our. of the Am. Rocket Soc., vol. 72, De- 1,994,249 Ipatiefi et a1. Mar. 12, 1935 cembgr 1947 age 21,

2,360,272 Plummer Oct. 10, 1944 10 

7. A METHOD FOR PRODUCING IMMEDIATE THRUST TO A ROCKET, COMPRISING INTRODUCING AN OXIDIZER, WHICH OXIDIZER IS CAPABLE OF CAUSING SPONTANEOUS IGNITION UPON CONTACT WITH A HYPERGOLIC FUEL, AND A FAST BURNING FUEL INTO SAID ROCKET IN A COMBUSTION ZONE THERIN IN CONTACT WITH EACH OTHER, THE STOICHOMETRIC RATIO OF OXIDIZER TO FUEL BEING WITHIN THE LIMITS FROM 0.5:1 TO 6:1, AND BURNING SAID FUEL IN SAID ROCKET WITH SAID OXIDIZER AT A HIGH BUT CONTROLLALE RATE, SAID FUEL CONTAINING FROM 1 TO 100 PERCENT OF A COMPONENT WHICH IS HYPERGOLIC IN THE PURE STATE WHEN CONTACTED WITH SAID OXIDIZER, SAID COMPONENT BEING AN ESSENTIAL INGREDIENT FOR IMPARTING SAID FAST BURNING QUALITY TO SAID FUEL BY ITS PRESENCE THEREIN, SAID COMPONENT BEING AT LEAST ONE OF THE MATERIALS SELECTED FROM THE GROUP CONSISTING OF (1) A CONJUGATED DIENE CHARACTERIZED BY THE STRUCTURAL FORMULA 